Among all programs that are open source, only a minuscule fraction
are not free. If the bottom row were drawn to scale, its text would
have to be in a tiny font, perhaps too small to read.

Tivoized or “tyrant” devices contain nonfree
executables made from source code that is free. As of 2013, many
Android devices are tyrants, but some are not.

“O” stands for “other” and refers to
programs whose source is under licenses which are open source but not
free. Several such licenses were written around 2000, and they were
used to release some programs. It has been a long time since we heard
of software released under those licenses. We don't know whether they
are still used.